1. Field of the Invention
This invention relates to an apparatus for and a process of extracting oxygen from fluids in which the oxygen is dissolved.
2. Description of the Prior Art
One of the primary problems which hinders man in his efforts to explore and develop the ocean realms is the lack of a ready supply of oxygen. In most of the world's oceans, the oxygen content of both shallow and deep waters is similar to that of surface water in equilibrium with air. Practical methods have not yet been devised for extracting and utilizing this vast amount of oxygen for the maintenance of man in an undersea environment. Fish, however, have obviously solved the problem of oxygen extraction from seawater. Fish species weighing well over a thousand pounds and burning metabolities at rates roughly comparable to that of man easily extract adequate dissolved oxygen from seawater for their varied activities. Moreover, many species of fish transfer oxygen from seawater into a gaseous state. These fish, ones that possess swim bladders, are able to pump and concentrate oxygen against enormous hydrostatic pressure gradients. In certain fish species oxygen is transported from the dissolved state in seawater, with a .sub..rho. O.sub.2 of 0.2 atmospheres, to a gaseous phase in the swim bladder where the .sub..rho. O.sub.2 may exceed 100 atmospheres.
Many attempts to develop methodologies of extracting oxygen from gaseous mixtures or water are known. Warne et al, U.S. Pat. No. 2,217,850, and Folger et al, U.S. Pat. No. 2,450,276, disclose processes of separating oxygen from other gases using solutions of cobalt compounds. However, these techniques would be ineffective in a liquid system, e.g., seawater, since the compounds are in solution and would be washed away if contacted with liquids rather than the disclosed gases. Miller, U.S. Pat. No. 3,230,045, discloses using oxygen-binding chromoproteins such as hemoglobin and hemocyanin to separate oxygen from other gases. The chromoproteins are kept moist or in solution and are immobilized on filter paper where they may be bound by a binder such as fibrin, and an electrolyte such as sodium chloride may be present. However, this technique would also be ineffective in a liquid system since the protein is not insoluble and thus would be washed away if water were allowed to flow through the system. Moreover, there is no provision for regeneration of oxidized (inactive) oxygen carriers that would be formed in this system. Bodell, U.S. Pat. No. 3,333,583, and Robb, U.S. Pat. No. 3,369,343, disclose apparatus for extracting oxygen from seawater using thin tubes of silicone rubber or a membrane of silicone rubber, respectively. However, neither the capillary networks nor the permeable membranes working alone have been found to be practicable in real-life situations. Isomura, U.S. Pat. No. 3,377,777, discloses concentrating oxygen from natural waters by equilibration with exhaled gases, i.e., by utilizing large areas of gas-water interface and simple diffusional considerations such that the partial pressure of the gas phase and the partial pressure of the liquid phase in the extraction zone provide for release of oxygen from the liquid phase into the gas phase and absorption of CO.sub.2 by the water phase. Additionally, the solubility of oxygen in seawater is decreased by heating the seawater, and this heating also increases the solubility of CO.sub.2. However, the heating of the seawater produces an energetically undesirable process. Rind, U.S. Pat. No. 4,020,833, discloses an oxygen source for closed environments comprising a mixture of a metallic superoxide, which releases oxygen upon contact with CO.sub.2 and water vapor, and a material which absorbs CO.sub.2. However, this system suffers from the defect of the capacity being limited by the bulk amount of mixture which can be carried, i.e., it is not capable of continuously producing oxygen without replenishment. Iles et al, U.S. Pat. No. 4,165,972, discloses separating oxygen from gas mixtures using metal chelates as sorbents. However, the technique is not extendable to the extraction of oxygen from water.
Artificial oxygen carriers and their properties in solution are described by a number of researchers. Traylor et al, "Solvent Effects on Reversible Formation and Oxidative Stability of Heme-Oxygen Complexes", J.A.C.S. 96, 5597 (1974) discloses the effect of solvent polarity on oxygenation of several heme-base complexes prepared by reduction with sodium dithionite or a mixture of Pd black and calcium hydride. Crumbliss et al, "Monomeric Cobalt-Oxygen Complexes", Science, 6, June 1969, volume 164, pp. 1168-1170, discloses Schiff base complexes of Co(II) which form stable cobalt-oxygen species in solution instead of cobalt-oxygen-cobalt bridged complexes. Crumbless et al, "Monomeric Oxygen Adducts of N,N'-Ethylenebis (acetylacetoniminato) ligand-cobalt(III): Preparation and Properties", J.A.C.S. 92, 55 (1970), discloses a series of monomeric molecular oxygen carriers based on cobalt ligand complexes. Dufour et al, "Reaction of Indoles with Molecular Oxygen Catalyzed by Metalloporphyrins", Journal of Molecular Catalysis, 1, 277 (1980), discloses the catalysis of the oxygenation of simple, alkyl-substituted indoles by Co(II), Co(III), and Mn(III) meso-tetraphenyl-porphines wherein a ternary complex O.sub.2 -CoTPP-indole is formed initially. Brault et al, "Ferrous Porphyrins in Organic Solvents: I. Preparation and Coordinating Properties", Biochemistry, 13, 4591 (1974), discloses the preparation and properties of ferrous deutereporphyrin dimethyl ester and ferrous mesotetraphenylporphine in various organic solvents. Chang et al, "Kinetics of Reversible Oxygenation of Pyrroheme-N-[3-(1-imidazolyl)propyl]amide", discloses studies on the oxygenation of pyrroheme-N-[3-(1-imidazolyl)-propyl]amide, i.e., a synthesized section of the myoglobin active site. Castro, "Hexa and Pentacoordinate Iron Poryhyrins", Bioinorganic Chemistry, 4, 45-65 (1974), discloses the direct synthesis of hexa and pentacoordinate iron porphyrins, i.e., the prosthetic groups for the active sites of certain cytochrome and globin heme proteins. Chang et al, "Solution Behavior of a Synthetic Myoglobin Active Site", J.A.C.S., 95, 5810 ( 1973), discloses studies on a synthesized section of the myoglobin active site and indicates that the oxygen binding reaction does not require the protein. Naturally occurring oxygen carriers have been chemically cross-linked and their properties described. Bonsen et al, U.S. Pat. No. 4,053,590, discloses a polymerized, cross-linked, stromal-free, hemoglobin proposed to be useful as a blood substitute. Morris et al, U.S. Pat. No. 4,061,736, discloses intramolecularly cross-linked, stromal-free hemoglobin. Wong, U.S. Pat. No. 4,064,118, discloses a blood substitute or extender prepared by coupling hemoglobin with a polysaccharide material. Mazur, U.S. Pat. No. 3,925,344, discloses a plasma protein substitute, i.e., an intramolecular, cross-linked hemoglobin composition. Other oxygen binding compounds are discussed in J. Amer. Chem. Soc., 105,6585 (1983), which is a review article discussing many such compounds; Macromolecules, 14,1153 (1981), which discusses so-called picket-fence porphyrins; and J. Amer. Chem. Soc., 94,5125 (1972), which discusses cobalt protoporphyrins with a 1-methylimidazole ligand as an oxygen binder.
An additional area of relevant prior art encompasses blood oxygenators. Many apparatus useful for extracorporeal blood oxygenation use oxygenpermeable membranes to supply oxygen to blood. Examples of patents which have issued or which have been published in this field include the following: PCT Published International Application No. 8100522 discloses a gas-permeable membrane and a blood oxygenator based on its use; British patent No. 1,570,917 discloses a blood oxygenator; German OS No. 2,851,776 (June 12, 1980) discloses a film-like selective permeable-membrane unit for mass transfer between fluids; U.S. Pat. No. 4,199,458 discloses a membrane diffusion device with external compression; U.S. Pat. No. 4,183,962 discloses oxygenating blood by the utilization of liquid membranes; published Netherlands patent application No. 7900345 discloses a liquid-membrane-forming apparatus; U.S. Pat. No. 4,151,088 discloses a membrane diffusion device; U.S. Pat. No. 4,110,220 discloses a mass transfer device useful for blood oxygenation; Japanese Kokai No. 7816365 discloses an apparatus for equilibrating solutions with various gases; USSR patent No. 577,037 discloses a membrane for artificial oxygenation of blood; French patent No. 2,315,283 discloses a method and apparatus for oxygenation of blood; U.S. Pat. No. 4,031,012 discloses a separatory apparatus useful for oxygenating blood; U.S. Pat. No. 3,996,141 discloses a dialysis membrane useful for blood oxygenation; U.S. Pat. No. 3,989,626 discloses a membrane transfer process and apparatus; British patent No. 1,442,754 discloses improvements in an apparatus for effecting mass transfer between fluids; British patent No. 1,447,174 discloses improvements in a membrane diffusion device; Canadian patent No. 1,156,414 discloses a microporous siloxane polymer membrane; Swedish patent No. 423,678 discloses a blood oxygenator; U.S. Pat. No. 4,353,799 discloses a hydrophobic diffusion membrane with a wettable surface useful for blood oxygenators; German OS No. 3,106,188 (Aug. 26, 1982) discloses an oxygenator membrane; published Australian patent specification No. 517,953 (Sept. 3, 1981) discloses a plate dialyser that can be used for blood oxygenation; Japanese Kokai No. 81132959 discloses an artificial lung; British patent No. 1,592,771 discloses an apparatus for mass transfer such as blood oxygenation; and French patent No. 2,478,482 discloses a gas-permeable membrane useful in blood oxygenation. In addition to these patents, many other publications related to the field of blood oxygenation can be found by a computer-assisted search of Chemical Abstracts data bases using the search terms "blood" and "oxygenation". Using the ORBIT system, these search phrases located 54 relevant publications in the 1982-present data base (CA82) and 113 relevant publications in the 1977-1981 data base (CA77).
Many of the prior art problems involving extraction of oxygen from fluids were overcome by the invention disclosed in U.S. Pat. Nos. 4,427,416 and 4,343,715, which disclose oxygen carriers which have been insolubilized at high concentrations by being entrapped and/or covalently linked to a polyurethane matrix or to comparable supports in states that are capable of reversible oxygen bonding and are regenerable in the event of oxidation. The material disclosed in these patents is generally known by the name "Hemosponge", since it is generally, though not necessarily, based on hemoglobin. The method and material as described in these patents are perfectly capable of extracting oxygen from various fluid environments in useful form, but the rate of extraction is less than that which may be desired for many applications which involve a high rate of oxygen use. Accordingly, there remains a need for an improved apparatus and method for the removal of oxygen from fluids.